Android加载asset的db

extends:http://blog.csdn.net/lihenair/article/details/21232887

项目需要将预先处理的db文件加载到数据库中，然后读取其中的信息并显示

加载数据库的代码参考了http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/

效果如下：

1. 将asset中的db文件复制到database数据库中

  

 
public class DBHelper extends SQLiteOpenHelper {  
  
    private static final String LOG_TAG = "DataHelper";  
      
    private SQLiteDatabase mDataBase;  
    private final Context mContext;  
      
    private static final String DATABASE_PATH = "/data/data/PACKAGE_NAME/databases/";  
    private static final String DATABASE_NAME = "xx.db";  
    private static final int DATABASE_VERSION = 1;  
  
    public DBHelper(Context context) {  
        super(context, DATABASE_NAME, null, DATABASE_VERSION);  
        this.mContext = context;  
    }  
  
    public DBHelper(Context context, String name, CursorFactory factory,  
            int version) {  
        super(context, name, factory, version);  
        // TODO Auto-generated constructor stub  
        this.mContext = context;  
    }  
  
    /** 
     * Creates a empty database on the system and rewrites it with your own 
     * database. 
     * */  
    public void createDataBase() throws IOException {  
  
        boolean dbExist = checkDataBase();  
          
        Log.d(LOG_TAG, "dbExist: " + dbExist);  
          
        if (dbExist) {  
            // do nothing - database already exist  
        } else {  
            // By calling this method and empty database will be created into  
            // the default system path  
            // of your application so we are gonna be able to overwrite that  
            // database with our database.  
            this.getReadableDatabase();  
  
            try {  
                copyDataBase();  
            } catch (IOException e) {  
                throw new Error("Error copying database");  
            }  
        }  
  
    }  
  
    /** 
     * Check if the database already exist to avoid re-copying the file each 
     * time you open the application. 
     *  
     * @return true if it exists, false if it doesn't 
     */  
    private boolean checkDataBase() {  
        Log.d(LOG_TAG, "checkDataBase");  
        SQLiteDatabase checkDB = null;  
  
        try {  
            String myPath = DATABASE_PATH + DATABASE_NAME;  
            checkDB = SQLiteDatabase.openDatabase(myPath, null,  
                    SQLiteDatabase.OPEN_READONLY);  
        } catch (SQLiteException e) {  
            // database does't exist yet.  
        }  
  
        if (checkDB != null) {  
            checkDB.close();  
        }  
        return checkDB != null ? true : false;  
    }  
  
    /** 
     * Copies your database from your local assets-folder to the just created 
     * empty database in the system folder, from where it can be accessed and 
     * handled. This is done by transfering bytestream. 
     * */  
    private void copyDataBase() throws IOException {  
        Log.d(LOG_TAG, "copyDataBase");  
        // Open your local db as the input stream  
        InputStream myInput = mContext.getAssets().open(DATABASE_NAME);  
  
        // Path to the just created empty db  
        String outFileName = DATABASE_PATH + DATABASE_NAME;  
  
        // Open the empty db as the output stream  
        OutputStream myOutput = new FileOutputStream(outFileName);  
  
        // transfer bytes from the inputfile to the outputfile  
        byte[] buffer = new byte[1024];  
        int length;  
        while ((length = myInput.read(buffer)) > 0) {  
            myOutput.write(buffer, 0, length);  
        }  
  
        // Close the streams  
        myOutput.flush();  
        myOutput.close();  
        myInput.close();  
  
    }  
  
    public void openDataBase() throws SQLException {  
        Log.d(LOG_TAG, "openDataBase");  
        // Open the database  
        String myPath = DATABASE_PATH + DATABASE_NAME;  
        mDataBase = SQLiteDatabase.openDatabase(myPath, null,  
                SQLiteDatabase.OPEN_READONLY);  
  
    }  
  
    @Override  
    public synchronized void close() {  
        if (mDataBase != null)  
            mDataBase.close();  
        super.close();  
  
    }  
  
    @Override  
    public void onCreate(SQLiteDatabase db) {  
        // TODO Auto-generated method stub  
    }  
  
    @Override  
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {  
        // TODO Auto-generated method stub  
    }  
  
}  

 

 

调用的代码如下：

  

DataBaseHelper myDbHelper = new DataBaseHelper();  
        myDbHelper = new DataBaseHelper(this);  
   
        try {  
            myDbHelper.createDataBase();  
    } catch (IOException ioe) {  
        throw new Error("Unable to create database");  
    }  
    try {  
        myDbHelper.openDataBase();  
    }catch(SQLException sqle){  
        throw sqle;  
    }  

 

 

2. 显示数据库中的内容 

 

public class CityGPS extends Activity {  
  
private static final String TAG = CityGPS.class.getSimpleName();  
  
private EditText mCityEdit;  
private TextView mNameText;  
private TextView mLattText;  
private TextView mLongText;  
private Button mButton;  
private ListView mList;  
private SimpleCursorAdapter mAdapter;  
private Cursor cursor = null;  
  
@Override  
protected void onCreate(Bundle savedInstanceState) {  
   super.onCreate(savedInstanceState);  
   setContentView(R.layout.main);  
  
   DBHelper mDbHelper = new DBHelper(this);  
  
   try {  
       mDbHelper.createDataBase();  
   } catch (IOException ioe) {  
       throw new Error("Unable to create database");  
   }  
  
   try {  
       mDbHelper.openDataBase();  
   } catch (SQLException sqle) {  
       throw sqle;  
   }  
  
   mCityEdit = (EditText) findViewById(R.id.city);  
   mNameText = (TextView) findViewById(R.id.name);  
   mLattText = (TextView) findViewById(R.id.lat);  
   mLongText = (TextView) findViewById(R.id.lon);  
  
  
   String sql = "SELECT * FROM citygps";  
   cursor = mDbHelper.getReadableDatabase().rawQuery(sql, null);  
  
   String[] strings = { "city", "lat", "lon" };  
   int[] ids = { R.id.name, R.id.lat, R.id.lon };  
   mAdapter = new SimpleCursorAdapter(this, R.layout.item, cursor,  
           strings, ids, 0);  
   mList = (ListView) findViewById(R.id.list);  
   mList.setAdapter(mAdapter);  
   mButton = (Button) findViewById(R.id.btn);  
   mButton.setOnClickListener(new OnClickListener() {  
  
  
       @Override  
       public void onClick(View v) {  
           // TODO Auto-generated method stub  
           String city = mCityEdit.getText().toString();  
  
  
           if (TextUtils.isEmpty(city) == true) {  
               Toast.makeText(CityGPS.this, "plz input city",
                       Toast.LENGTH_SHORT).show();  
               return;  
           }  
  
  
           String[] projection = { CityGPSTable.CITY,  
                   CityGPSTable.LATITUDE, CityGPSTable.LONGITUDE };  
           String selection = CityGPSTable.CITY + " = " + "\"" + city + "\"";  
           Cursor cursor = getContentResolver().query(  
                   CityGPSContentProvider.CONTENT_URI, projection, selection,  
                   null, null);  
  
           if (cursor != null) {  
               cursor.moveToFirst();  
               Float lat = cursor.getFloat(cursor.getColumnIndex(CityGPSTable.LATITUDE));  
               Float lon = cursor.getFloat(cursor.getColumnIndex(CityGPSTable.LONGITUDE));  
                 
               Log.d(TAG, "lat: " + lat + " lon: " + lon);  
  
               mNameText.setText(city);  
               mLattText.setText(lat.toString());  
               mLongText.setText(lon.toString());  
           }  
       }  
   });  
}  
}  

 

 

main.xml 

 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    xmlns:tools="http://schemas.android.com/tools"  
    android:layout_width="match_parent"  
    android:layout_height="match_parent"  
    android:orientation="vertical"  
    tools:context=".CityGPS" >  
  
  
    <LinearLayout  
        android:layout_width="match_parent"  
        android:layout_height="wrap_content"  
        android:orientation="horizontal" >  
  
  
        <EditText  
            android:id="@+id/city"  
            android:layout_width="0dip"  
            android:layout_height="wrap_content"  
            android:layout_weight="1"  
            android:ems="10"  
            android:inputType="text" />  
  
  
        <Button  
            android:id="@+id/btn"  
            android:layout_width="wrap_content"  
            android:layout_height="wrap_content"  
            android:text="@string/search" />  
    </LinearLayout>  
  
  
    <LinearLayout  
        android:layout_width="match_parent"  
        android:layout_height="wrap_content"  
        android:orientation="horizontal" >  
  
  
        <TextView  
            android:id="@+id/name"  
            style="@android:style/TextAppearance.Holo.Medium"  
            android:layout_width="0dip"  
            android:layout_height="wrap_content"  
            android:layout_weight="1"  
            android:hint="@string/city" />  
  
  
        <TextView  
            android:id="@+id/lat"  
            style="@android:style/TextAppearance.Holo.Medium"  
            android:layout_width="0dip"  
            android:layout_height="wrap_content"  
            android:layout_weight="1"  
            android:hint="@string/lat" />  
  
  
        <TextView  
            android:id="@+id/lon"  
            style="@android:style/TextAppearance.Holo.Medium"  
            android:layout_width="0dip"  
            android:layout_height="wrap_content"  
            android:layout_weight="1"  
            android:hint="@string/lon" />  
    </LinearLayout>  
  
  
    <View  
        android:layout_width="match_parent"  
        android:layout_height="3dp"  
        android:background="@android:color/holo_red_dark"  
        android:visibility="visible" />  
  
  
    <ListView  
        android:id="@+id/list"  
        android:layout_width="match_parent"  
        android:layout_height="0dip"  
        android:layout_weight="1" />  
  
  
</LinearLayout>  

 

 

item.xml，每行都带分割线

  

 
<?xml version="1.0" encoding="utf-8"?>  
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    android:layout_width="match_parent"  
    android:layout_height="match_parent"  
    android:orientation="horizontal" >  
  
    <TextView  
        style="@android:style/TextAppearance.Holo.Medium"  
        android:id="@+id/name"  
        android:layout_width="0dip"  
        android:layout_height="wrap_content"  
        android:layout_weight="1"  
        android:hint="@string/city" />  
      
    <View  
        android:layout_width="1px"  
        android:layout_height="match_parent"  
        android:background="#B8B8B8"  
        android:visibility="visible" />  
  
    <TextView  
        style="@android:style/TextAppearance.Holo.Medium"  
        android:id="@+id/lat"  
        android:layout_width="0dip"  
        android:layout_height="wrap_content"  
        android:layout_weight="1"  
        android:hint="@string/lat" />  
  
    <View  
        android:layout_width="1px"  
        android:layout_height="match_parent"  
        android:background="#B8B8B8"  
        android:visibility="visible" />  
      
    <TextView  
        style="@android:style/TextAppearance.Holo.Medium"  
        android:id="@+id/lon"  
        android:layout_width="0dip"  
        android:layout_height="wrap_content"  
        android:layout_weight="1"  
        android:hint="@string/lon" />  
  
</LinearLayout>